Loudspeaker system



March 17, 1970 u. L. LAHTI LOUD-SPEAKER SYSTEM Filed Dec. 4, 1968INVENTOR UDLEVI L. LAHTl ATTORNEKS United States Patent 3,500,953LOUDSPEAKER SYSTEM Uolevi L. Lahti, 909 Sunset Road,

Ann Arbor, Mich. 48103 Filed Dec. 4, 1968, Ser. No. 781,133 Int. 'Cl. Gk13/00; H04r 7/16 U.S. Cl. 18131 2 Claims ABSTRACT OF THE DISCLOSURE Aloudspeaker system including an enclosure containmg a downwardlydirected low frequency loudspeaker provided with an inverted exponentialhorn, and an upwardly directed high frequency loudspeaker provided witha convex reflector which is adjustable in both height and angle of tilt,and which may include a pre-stressed soft reflecting surface.

BACKGROUND OF THE INVENTION The problem of providing a high fidelityloudspeaker system which occupies small space, yet which can if calledon to do so, provide 360 coverage, is a perennial one, as is the problemof providing low frequency response in a small volume speaker. It isthis problem to which the present invention addresses itself.

SUMMARY OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is aview in front elevation of a preferred embodiment of the invention;

FIGURE 2, is a view in section taken on the line 2-2 of FIGURE 1;

FIGURE 3 is a view in section taken on the line 3--3 of FIGURE 2; and

FIGURE 4 is a view in section of a modification of the system of FIGURES1-3, employing a cylindrical in place of a spherical enclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGURES 1-3 isillustrated a spherical enclosure 10 preferably fabricated of flexibleresinous sheet material. Enclosure 10 is mounted on a standard 11, whichincludes a circularly arcuate support 12 which faces concavely upwardfor less than 180, and which contains pivotal supports 13, 14, adjacentits ends. Enclosure 10 is pivotally mounted on the supports 13, 14 sothat it is susceptible of tilting. Mounted internally of enclosure 10and normally directed downwardly is a low frequency loudspeaker orwoofer 15. The back of the speaker is air loaded in the usual manner, asby glass wool or cotton 16. The front end of the speaker, 17, isprovided with an inverted exponential horn 18, which proceeds to anopening 19 in enclosure 10.

The effect of the horn is known. It loads the front end of the speaker,thereby improving and extending low frequency response, provides animproved acoustic load and matching, and spreads the acoustic radiationpattern.

The loading appears to remove resonances, so that very low frequencyhigh fidelity response is achieved, despite use of a small enclosure. Inthe present invention the sound is downwardly directed toward a floor,which may be carpeted. Nevertheless, good azimuthal spread of theacoustic pattern is achieved, and can be achieved over 360. Should it bedesired that radiation be directional, the sphere 10 can be tilted todirect horn 15 generally horizontally, or at any angle intermediatevertical and horizontal, or above horizontal, there being no restrictionprovided to tilt by the pivots 13, 14.

Normally directed vertically is a tweeter 20, and loaded in theenclosure 10, but not provided with a horn. The permanent magnet 21 ofthe tweeter 20 is divided vertically to slidably accept a rod 22. Enoughfriction is provided to maintain the rod 22 in any adjusted position.Atop the rod 22 is secured a ball 24 and to the ball is secured a convexreflector, 25, tiltable about the ball 24 in a wide range of degrees anddirections. The reflector 25 is fabricated of two discs of resilientplastic sheet, 26 and 27, joined at their edges 28. A small guidecylinder 29 joins the centers of the discs and contains a compressionspring 30 and into which and against spring 30, protrudes the major partof ball 24, a minor part extending beyond the disc 27 via a tightopening 32. The spring acts to prevent flopping and assures smoothmovement of the reflector 25 on the ball by providing friction and alsomaintains the convexity of the discs 26, 27 by tending to spread them.If the edge 28 is horizontal the disc 27 spreads sound in all directionsazimuthally. But, by tilting reflector 25 and adjustin its height,directivity may be achieved, or enhanced directivity in preferreddirections.

In FIGURE 4 is illustrated a modification of the invention employing acylindrical enclosure on a vertical axis. This lacks the element ofpositional adjustability of the woofer and tweeter, but all otherfeatures of the system of FIGURES 1-3 are present, which are not furtherdescribed since to do so would be superfluous.

What I claim is:

1. A loudspeaker system including an enclosure having a normallyvertical axis, a low frequency loudspeaker mounted in said enclosure anddirected downwardly,

an inverted exponential horn coupling said loudspeaker to atmosphere,

at high frequency loudspeaker mounted in said enclosure and directedupwardly, a convex reflector mounted above said high frequencyloudspeaker, and means mounting said reflector for vertical adjustmentand for angular tilt adjustment with respect to said loudspeaker, saidreflector including a convex surface as seen from said high frequencyloudspeaker of approximately the transverse dimensions of said highfrequency loudspeaker.

2. The combination according to claim 1, wherein said high frequencyloudspeaker includes an axial permanent magnet, and means mounting saidreflector is a said rod extending through said magnet and slidabletherein, and wherein a ball is mounted atop said rod, said reflectorbeing tiltably mounted on said ball.

References Cited UNITED STATES PATENTS 2,065,367 12/1936 Evans 18l313,329,235 7/1967 Shaper .18l3l FOREIGN PATENTS 700,630 12/1964 Canada.

STEPHEN J. TOMSKY, Primary Examiner

